Heliox

[Valyngar]

Any reason why not to dive in 20-45 meter with heliox compared to nitrox/helitrox. With CC cost is negletable. Bit colder to dive with? Was thinking building heliox fill station with booster and o2 and he.

 

[rjack321]

Any reason why not to dive in 20-45 meter with heliox compared to nitrox/helitrox. With CC cost is negletable. Bit colder to dive with? Was thinking building heliox fill station with booster and o2 and he.

Just don't put it in your drysuit.

 

[njdiverjoe]

Any reason why not to dive in 20-45 meter with heliox compared to nitrox/helitrox. With CC cost is negletable. Bit colder to dive with? Was thinking building heliox fill station with booster and o2 and he.

I've done a fair amount of heliox diving in ranges a bit deeper than you listed. For those depths I don't think you will notice much difference between heliox and say 10/50.

If you want to go with heliox -- something you might think about is how you want to plan your deco and bailout.

 

[Valyngar]

Just don't put it in your drysuit.

Well yeah ofc other gas for drysuit or you would be freezing. But does make you colder if you only breathe it?

 

[rjack321]

Well yeah ofc other gas for drysuit or you would be freezing. But does make you colder if you only breathe it?

There is no affect breathing it. No matter what you breath your lungs will warm it to body temp and 100% humidity. In theory you might lose less heat breathing trimix because it takes fewer calories to raise its temperature. In practice it makes no difference

 

[wedivebc]

Well yeah ofc other gas for drysuit or you would be freezing. But does make you colder if you only breathe it?

Breathing helium mixtures will not make you colder, in fact the lower specific heat means it is probably removing less heat from your body than other gasses you are likely to breathe.

 

[_Ralph]

Breathing helium mixtures will not make you colder, in fact the lower specific heat means it is probably removing less heat from your body than other gasses you are likely to breathe.

OC I can definitely tell the difference in the coldness of breathing gas. Even the 10% difference beteeen 21/35 and 18/45 makes my throat chilly


Edit: d’oh didn’t notice talking CC .....

_R

 

[wedivebc]

OC I can definitely tell the difference in the coldness of breathing gas. Even the 10% difference beteeen 21/35 and 18/45 makes my throat chilly


Edit: d’oh didn’t notice talking CC .....

_R

if feels colder on your throat because helium is a good conductor of heat, not becaue the helium is taking heat from your body. Heat and temperature are related but different.

 

[fsardone]

If you want to go with heliox -- something you might think about is how you want to plan your deco and bailout.

This ^^^^
I'd be very wary if bailing out to anything different than heliox.
This is becuase of Isobaric Counter Diffusion. Especially if diving shallow the amount of oxygen in the breathed mix will be very high and therefore the space available to add nitrogen tiny (remember the 1 to 5 rule increase nitrogen no more than one fifth of the helium decrease the rest needs to be oxygen).

To have an idea how little you have to play with you can use a calculator I put together to determine the breathed gas composition.
Fill only the blue shaded cell and do not worry about the div by zero error in the He/N2 ratio cell.
Also do not rely on the density values you can use the calculator in this other post for that.

Hello RainPilot,
I was rereading through this thread (I find re-reading things useful to better understanding, Thanks Simon for posting here), and I thought using as a basis your exel file to develop a spreadsheet that ,given diluent and setpoint, would calculate breathing gas density at depth for CCR.

View attachment 474965

 

[Valyngar]

Yeah thanks for tips. Would have change bailouts for Heliox mixes too. So no n2 on any gasses. Well bailout fill is just one time cost. 50 liter 300 bar helium is bit less than 400 euros here and O2 50 liter 200 bar is about 50 euros.